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1// SPDX-License-Identifier: GPL-2.02// Copyright (c) 2019 Facebook3 4#include <stdint.h>5#include <string.h>6 7#include <linux/stddef.h>8#include <linux/bpf.h>9 10#include <bpf/bpf_helpers.h>11 12#include "bpf_compiler.h"13#include "bpf_misc.h"14 15/* Max supported length of a string with unsigned long in base 10 (pow2 - 1). */16#define MAX_ULONG_STR_LEN 0xF17 18/* Max supported length of sysctl value string (pow2). */19#define MAX_VALUE_STR_LEN 0x4020 21const char tcp_mem_name[] = "net/ipv4/tcp_mem";22static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)23{24 unsigned char i;25 char name[sizeof(tcp_mem_name)];26 int ret;27 28 memset(name, 0, sizeof(name));29 ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);30 if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)31 return 0;32 33 __pragma_loop_unroll_full34 for (i = 0; i < sizeof(tcp_mem_name); ++i)35 if (name[i] != tcp_mem_name[i])36 return 0;37 38 return 1;39}40 41SEC("cgroup/sysctl")42int sysctl_tcp_mem(struct bpf_sysctl *ctx)43{44 unsigned long tcp_mem[3] = {0, 0, 0};45 char value[MAX_VALUE_STR_LEN];46 unsigned char i, off = 0;47 volatile int ret;48 49 if (ctx->write)50 return 0;51 52 if (!is_tcp_mem(ctx))53 return 0;54 55 ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);56 if (ret < 0 || ret >= MAX_VALUE_STR_LEN)57 return 0;58 59 __pragma_loop_unroll_full60 for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {61 ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,62 tcp_mem + i);63 if (ret <= 0 || ret > MAX_ULONG_STR_LEN)64 return 0;65 off += ret & MAX_ULONG_STR_LEN;66 }67 68 69 return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];70}71 72char _license[] SEC("license") = "GPL";73